# Manure Application Rate Calculator

> Find the manure or slurry rate that supplies a nutrient target, from the manure’s nutrient content and first-year availability, in t/ha, tons/acre or gal/acre.

Category: Agriculture · Applies to: Worldwide · Last updated: 2026-10-29
Interactive calculator: https://calculators.geekmidst.com/calculators/manure-application-rate-calculator

Divide the nutrient the crop needs by the plant-available nutrient in each tonne (or cubic metre) of manure to get the application rate.

Also called: Slurry rate calculator, Manure nutrient calculator.

## Inputs
- Nutrient to supply (default 100)
- Target unit (options: kg/ha, lb/acre; default kg_ha)
- Nutrient content of the manure (default 6)
- Content unit (options: kg per tonne (solid), lb per US ton (solid), kg per m³ (liquid), lb per 1,000 US gal (liquid); default kg_t)
- Available in the first year (unit %; default 40)
- Field area (default 2)
- Area in (options: Acres, Hectares; default ha)

## Results
- Rate per hectare (t or m³)
- Rate per acre (t or m³)
- Rate per acre (US tons or US gal)
- Manure for the field (t or m³)
- In words

## Formula

```
Rate = Nutrient target ÷ (Nutrient content × Availability %);  Total = Rate × Area
```

Where:
- Nutrient content: kg per tonne or per m³ (lb/US ton × 0.5 = kg/t; lb/1000 gal × 0.1198 = kg/m³)
- Availability: first-year plant-available fraction

## Worked example
1. Available N = 6 kg/t × 0.40 = 2.4 kg per tonne.
2. Rate = 100 ÷ 2.4 = 41.67 t/ha (16.86 t or 18.59 US tons per acre).
3. For 2 ha: 83.33 t.

**Result:** To supply 100 kg/ha of available N from manure with 6 kg N/t at 40% availability, spread about 42 t/ha, 83 t on 2 ha.

## What the result means

Manure rarely matches crop needs for every nutrient. Check the P and K this rate supplies and top up the shortest nutrient with mineral fertiliser rather than adding more manure.

## Assumptions and limits
- Nutrient content is per unit of manure as spread (fresh weight).
- Local rules may cap manure or nitrogen rates (for example, in nitrate-vulnerable zones); check them before spreading.
- Availability figures are estimates that vary with timing and incorporation.

## Questions

### Why include availability?

Much of the nitrogen in manure is organic and only becomes available over several seasons, so only part counts towards this crop.

### Should I base the rate on N or P?

Where phosphorus builds up in soil, advisers often recommend rating manure on P and supplying the extra N from fertiliser.

## Related calculators
- [Fertiliser Application Rate Calculator](https://calculators.geekmidst.com/calculators/fertilizer-application-rate-calculator)
- [Fertiliser NPK Calculator](https://calculators.geekmidst.com/calculators/fertilizer-npk-blend-calculator)
- [Compost Volume Calculator](https://calculators.geekmidst.com/calculators/compost-volume-calculator)

Source: GM¹X CalcVerse — https://calculators.geekmidst.com/calculators/manure-application-rate-calculator